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'Cardiac Glycosides' in keywords
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1988 (1)
1979 (1)
1Author    HorstW. AlterRequires cookie*
 Title    Permeability of Plasma Membrane Vesicles to Ouabain and Mg2+ as a Factor Determining Rate of Binding of Ouabain to Na+ and K+ Dependent ATPase  
 Abstract    N a+, K+-ATPase of the plasma membrane isolated from sheep kidney medulla exhibits functio­ nal asymmetry for the cardiac glycoside ouabain. In this vesicular membrane preparation the rate of binding o f ouabain was slow (time constant > 60 min) when the vesicles were incubated in the presence o f isotonic sucrose. Upon treatment o f the preparation with hypoosmotic shock or phos-pholipase A the initial rate of ouabain binding was enhanced at least 3 fold. In equilibrium a concentration of the ouabain-enzyme-complex was obtained which was about twofold that of the untreated vesicles. This result suggests two types o f ouabain binding sites with an approximate stoichiometry of 1 to 1. The stoichiometry seems to be maintained at high concentrations of ouabain where binding curves show a biphasic time course. Additional information about hetero­ geneity of binding sites comes through experiments in which the vesicles were treated with Mg2+ prior to the addition o f ouabain. A minor fraction of the binding sites were occupied by ouabain only after longtime incubation with Mg2+. 
  Reference    Z. Naturforsch. 34c, 1224 (1979); received July 13/August 18 1979 
  Published    1979 
  Keywords    N a+, K+-ATPase, Plasma Membrane Vesicles, Cardiac Glycoside, Magnesium, Tightness 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-1224.pdf 
 Identifier    ZNC-1979-34c-1224 
 Volume    34 
2Author    Maike Petersen, Ulrich Hanns, Seitz, Ernst ReinhardRequires cookie*
 Title    Characterization and Localization of Digitoxin 12 ß-Hydroxylase from Cell Cultures of Digitalis lanata EHRH  
 Abstract    The cytochrome P-450-dependent monooxygenase digitoxin 12ß-hydroxylase from cell cultures of Digitalis lanata needs NADPH and molecular oxygen and hydroxylates cardiac glycosides with the aglycon of digitoxigenin to the corresponding derivatives of the C-series. Other electron donors cannot replace NADPH. The apparent K" m -values are 26 UM for NADPH, 7.1 ^IM for ß-methyldigitoxin and 10 ^IM for digitoxin. The reaction is inhibited by NADP + and cytochrome c in a competitive mode. The optimum temperature was at 20 °C. Low concentrations of Mn 2+ , Mg 2+ , and EDTA were slightly stimulatory, but there was no strict dependence on divalent cations. Digitoxin 12ß-hydroxylase is very stable at room temperature and the reaction proceeds for more than 20 h. After the addition of 15% glycerol, 70% of the original activity can be retained subsequent to freezing at —18 °C. By means of linear sucrose gradient fractionation of cellular membranes the digitoxin 12ß-hydroxylase was found to be located in the endoplasmic reticulum. 
  Reference    Z. Naturforsch. 43c, 199—206 (1988); received December 8 1987 
  Published    1988 
  Keywords    Cardiac Glycosides, Cytochrome P-450, Digitalis lanata, Digitoxin 12ß-Hydroxylase, Endoplas-mic Reticulum 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0199.pdf 
 Identifier    ZNC-1988-43c-0199 
 Volume    43